Various types of organic compounds have been used to advantageously alter certain properties of wet hydraulic cement compositions. One class of components, which can collectively be called “superplasticizers” fluidify or plasticize the wet cement composition to obtain a more fluid composition. A controlled fluidity is desired, such that the aggregate used in mortars and concretes does not segregate from the cement paste. Alternatively, superplasticizers may allow the cement composition to be prepared using a lower water to cement ratio in order to obtain a composition having a desired consistency which often leads to a hardened cement composition having a higher compressive strength development after setting.
A good superplasticizer should not only fluidify the wet cement composition to which it is added, but also maintain the level of fluidity over a desired period of time. This time should be long enough to keep the wet cement composition fluid, e.g. in a ready-mix truck while it is on its way to a job site. Another important aspect relates to the period for discharging the truck at the job site and the period needed for the cement composition for being worked in the desired final form. On the other side, the cement mixture cannot remain fluid for a too long time, that means the set must not greatly be retarded, because this will slow down the work on the job and show negative influences on the characteristics of the final hardened products.
Conventional examples of superplasticizers are melamine sulfonate/formaldehyde condensation products, naphthalene sulfonate/formaldehyde condensation products and lignosulfonates, polysaccharides, hydroxycarboxylic acids and their salts and carbohydrates.
In most cases, fluidizing agents are multi-component products with copolymers based on oxyalkylenglykolalkenylether and unsaturated dicarboxylic acid-derivatives as most important species. The European Patent EP 0 736 553 B1 discloses such copolymers comprising at least three sub-units and especially one unsaturated dicarboxylic acid derivative, one oxyalkylenglykolalkenylether and additionally one hydrophobic structural unit, such as ester units. The third structural unit can also be represented by polypropylenoxid- and polypropylenoxid-polyethylenoxid-derivatives, respectively.
The German published application DE 195 43 304 A1 discloses an additive for water containing mixtures for the construction field comprising a) a water-soluble sulfonic acid-, carboxylic- or sulfate group containing cellulose derivative, b) a sulfonic acid- and/or carboxylic acid containing vinyl-(co)-polymer and/or a condensation product based on aminoplast-builders or acryl containing compounds and formaldehyde. This additive shall show sufficient water retention ability and rheology-modifying properties. Therefore, this additive shall be suitable for construction chemical compositions containing cement, lime, gypsum, anhydrite and other hydraulic binder components.
Disclosed are also copolymers of ethylenically unsaturated ethers that can be used as plasticizers for cement containing mixtures (EP 0 537 870 A1). These copolymers contain an ether co-monomer and as additional co-monomer an olefinic unsaturated mono-carboxylic acid or an ester or a salt thereof, or alternatively an olefinic unsaturated sulfuric acid. These copolymers show a very short ether side chain with 1 to 50 units. The short side chain shall cause a sufficient plasticizing effect of the copolymers in cement containing masses with a reduced slump loss of the construction chemicals mass itself.
Based on the different characteristics and the availability of the superplasticizers mentioned above, it has been further desired to come up with new superplasticizers which are an improvement over the current state of the art. It is thus an object of this invention to provide new additives for hydraulic binder containing compositions which impart to wet binder compositions excellent slump and slump retention over the time. An additional aspect is an aqueous binder suspension with sufficient workability. Furthermore, the properties, the performance and effects of the provided copolymer shall be arbitrary.